Energy Reduction through Chiller Upgrades
Sirus, designed, managed and self-delivered a full primary plant upgrade for a long-standing client. The Mechanical Services and BMS in the building have been maintained by Sirus for the past 10 years.
Sirus also manage the energy metering for the building on behalf of the building facility management company.
The M50 Building is multi-tenanted, where each tenant is paying a percentage of the overall HVAC energy bill. Low-Pressure Hot Water (LPHW) and Chilled Water (CHW) delivered to each
The largest electrical loads for the building were the two existing RC Screw chillers, where these chillers were at end of life and were becoming unreliable.
The main aims for this project were:
- To reduce the building energy profile and carbon footprint.
- To provide a reliable & efficient delivery of LPHW & CHW energy.
- The primary chiller is a 540kW Turbocor, magnetic bearing, oil-free chiller.
- The secondary chiller is a 570kW screw chiller.
The mixed pair was selected to maximise the clients return on investment and overall cost of ownership for the life cycle of the machines.
As the Turbocor chiller‘s highest efficiency is at part load, the BMS system with BACnet interface to the chillers, are utilised to manage the staging of both chillers to keep the optimum loading to suit the building cooling load.
The upgrade also included the replacement of 2 No. 500 kW Sectional cast iron boilers, with a 6 cascade boiler system. The increased turndown ratio of this boiler arrangement, in conjunction with the improved BMS control on loading, improves efficiency and operation of the heating system, while also giving greater redundancy.
By using the Turbocor chiller and with the much-improved control, the chilled water generation has been greatly optimised.
By selecting the mixed pair instead of a matched pair, we delivered the maximum efficiency along with a reduced cost of ownership for our client.
Maintenance costs are greatly reduced as the Turbocor compressors require no servicing, so the only part to be replaced during its lifetime is the capacitor bank, after 10 years.
The chilled water energy costs to our client reduced by approximately 60% in the first six months of operation when comparing with metered data from the previous year. This resulted in the electrical energy provider having to adjust the building max demand profile, as the building came down to the low level cut off, for the tariff scheme. Previously the building operated closer to the max level.
The operation of the boilers will help reduce the buildings carbon footprint through the reduction of gas usage by the LPHW boilers. Gas consumption reduced by approximately 20% when comparing the gas meter bills for 2016 & 2017. When comparing data obtained from energy bills between December 2016 & December 2017, there was a reduction of nearly 3,000 m3 (33,300 kWh) of gas use which equates to approximately 6.8 tonnes CO2 saved. However, the real savings will be seen in the summer operation when the cascade boilers will be able to ramp down and operate more efficiently as the boilers are modular.
With these two chiller units in operation, it is expected that this project will reduce the carbon footprint of the building by over 61 tonnes CO2e by year end. In the first six months of operation alone, the chillers saved approx. 57,500 kWh electricity (30.59 tCO2e) in comparison to the previous year. The savings will primarily come from the chiller units, where they have not been operated in summer conditions yet and hence, the real savings from the new chiller configuration has yet to be discovered. However, we can approximate the emission reductions with the current data and recorded historical operation data of the previous chillers in the building to get a load profile.
Reduction in kWh